Display quality of a projection device may be directly affected by light emission quality and service life of a projection light source.
Laser light may be used to excite fluorescent powder to emit fluorescence of required color, so as to achieve conversion of light beam color. For example, a device for converting wavelength may be a fluorescent powder wheel. Partial area of the fluorescent powder wheel may be coated with a fluorescent powder layer of required color (hereinafter referred to as a fluorescent area), such as an area coated with red and green fluorescent powder. Partial area of the fluorescent powder wheel may be a transmitting area. When the device for converting wavelength is rotated at a high speed, if blue laser light is incident on the fluorescent powder layer, the fluorescent powder layer may be excited by the blue laser light in a way that a fluorescence beam may be generated. Color of the fluorescence beam may be the same as that of the fluorescent powder. If the blue laser light is incident on the transmitting area, the blue laser light may be transmitted. In this way, laser light of different colors may be generated successively. Since all blue laser light is incident on an irradiated area of the fluorescent powder wheel, a large amount of heat may be generated in the irradiated area of the fluorescent powder wheel, and temperature of the fluorescent powder may be extremely high. Under such a high temperature, efficiency of blue excitation light being converted into fluorescence beam by the excited fluorescent powder may be lowered. Aging of the fluorescent powder may be accelerated. Light emission quality and service life of the projection light source may be reduced.